Historically, New York City has had the largest number of heroin users in the U.S. (approximately 250,000). There is a need for a much clearer scientific understanding of prescription opioid (PO) medical use, misuse, and diversion among street drug users. The number of opioids available via prescription has increased, as have reports of their misuse. Street drug users are at high risk for misusing and illegally diverting POs, though this population may also use POs for appropriate medical reasons. There has been no broad-based longitudinal research with this significant population of drug users to determine the extent of PO use, misuse and diversion over time. An updated pilot study of over 700 NYC street drug users through 2006 found that nearly 90% used POs in their lifetimes and 60% used POs in the past month. OxyContin, Vicodin, and street methadone were the most often used, misused, and sold/diverted;the study found considerable variation in reasons for use, modes of use, and sources of POs. The proposed research aims to clarify the various motivations for PO use (e.g. pain relief, withdrawal avoidance, euphoria), routes of ingestion (e.g. oral as indicated, sniff/snort, injection), sources of supply (e.g. physicians/pharmacists, street dealers, family), and diversion/resale (e.g. use by someone else, resold, heroin substitute). The study will also document the impact of various regulatory policies to prevent misuse and diversion of POs. Social network theory provides the conceptual framework;this study will include a basic network analysis, comparing heroin and cocaine users'/sellers'networks with those predominantly using POs. Ethnographic data will complement the quantitative reports of resale activity. AIM A (Medical Use and Non-medical Misuse): Document and analyze patterns of PO consumption among street drug users in NYC. AIM B: Analyze the routes of diversion and markets for POs among street drug users in NYC. 500 street drug users will be interviewed regarding their use, misuse, and diversion of POs and followed-up after 6 months. 100 street drug users who report systematic diversion of POs will be interviewed in detail regarding episodes of diversion. Statistical analyses will document associations among other drug use, medical use of POs, and various forms of PO misuse. The research will provide systematic, longitudinal evidence about the extent of medical use, misuse, and diversion of POs within this population to help inform drug abuse control efforts.